Heart
rate changes are related to many factors including gender. The
autonomic changes accompanying emotion is the result of the activity of higher
brain centres, which are responsible for analysing emotionally relevant
stimuli. Studies examining the impact of
changes in the level of female ovarian hormones on cardiac autonomic ragulation
have produced inconsistent results. The purpose of the study was to
determine whether there is a menstrual cycle effect on heart rate changes elicited
by visual stimuli of different attractiveness. 12 healthy regularly cycling
females (age 21-28 years) during the follicular phase and 12 females during the
luteal phase have participated in the study. 90 pictures were selected from
International Affective Pictures System (IAPS) including 30 neutral, 30
pleasant and 30 unpleasant pictures. Stimuli were presented by E-prime software
and physiological data (heart rate) was collected using Biopac MP35 system. The
duration of the experimental session was approximately 15 minutes. Salivary
estradiol and progesterone levels were measured using an enzyme-linked
immunosorbent assay (ELISA).Progesterone
levels were found to be significantly higher in the luteal phase group (208.25
±123.63 pg/mL) than in the follicular phase group (67.22 ±49.85 pg/mL),
p<0.01. There were no significant differences in the salivary estradiol
levels between the follicular and the luteal groups. Heart rate deceleration elicited
by affective stimuli (duration 6s) comparing with the baseline period (1 minute
before images presentation) was significantly stronger in the luteal phase
group than in the follicular phase group, p=0.03. Different researchers have indicated that cardiac deceleration is the common response
to unpleasant visual stimuli. Our results showed that heart rate deceleration
was stronger in the luteal phase group than in the follicular phase group independently
of the valence of pictures, although unpleasant pictures caused the largest
changes.